I've just learned something about leather meal. I had always thought leather meal was made from virgin hides, but no. It is the floor sweepings from the leather tanning industry. Thus it contains chromium and way more than I want in my garden!
I have never specifically suggested anyone use leather meal in their garden but I have included it in my list of organic materials. No more of that!
Here is a website for those who want more info. I'll also quote the conclusion from that website.
http://www.omri.org/leather_meal.pdf
Quote:
Conclusion
The reviewers agree in the determination that leather meal that is a by-product of a chrome tanning process is a synthetic substanceand that it should be prohibited for use in organic agriculture. The reviewers agree that there are many alternatives available to this product. Although reviewers have mixed opinions about the dangers posed by addition of chromium(III) to the soil, they agree that addition of metals not required for plant nutrients is contrary to organic principles and NOSB recommendations. In addition, other metals such as lead, as well as solvents, preservatives, dyes, and other additives from the production process pose concerns.
The chrome, by the way, is used as an antimicrobial agent to keep the tanned leather from ever deteriorating. So you can see how it would actually be harmful to your soil microbes.
The report also says that the chrome in the leather is not available to plants. Well, that's nice in a shallow theory. Part of the beauty of organic soils is the humic acids have a way of making unavailable elements and minerals suddenly available in spades! Now I see it works both ways.